Evidence of altered central nervous system development in infants with iron deficiency anemia at 6 mo: delayed maturation of auditory brainstem responses

Abstract

Iron deficiency anemia has long been thought to have effects on the central nervous system (CNS). Finding direct evidence of this in human infants, however, has been challenging. Auditory brainstem responses (ABRs) provide a noninvasive means of examining an aspect of the CNS that is rapidly maturing during the age period when iron deficiency is most common. ABRs represent the progressive activation of the auditory pathway from the acoustic nerve (wave I) to the lateral lemniscus (wave V). The central conduction time (CCT, or wave I-V interpeak latency) is considered an index of CNS development because myelination of nerve fibers and maturation of synaptic relays lead to an exponential reduction in the CCT from birth to 24 mo. In 55 otherwise healthy, 6-mo-old Chilean infants (29 with iron deficiency anemia and 26 nonanemic control infants), the CCT was longer in those who had been anemic at 6 mo, with differences becoming more pronounced at 12- and 18-mo follow-ups despite effective iron therapy. The pattern of results--differences in latencies but not amplitudes, more effects on the late ABR components (waves III and V), and longer CCTs (as an overall measure of nerve conduction velocity)--suggested altered myelination as a promising explanation, consistent with recent laboratory work documenting iron's essential role in myelin formation and maintenance. This study shows that iron deficiency anemia in 6-mo-old infants is associated with adverse effects on at least one aspect of CNS development and suggests the fruitfulness of studying other processes that are rapidly myelinating during the first 2 y of life.

Iron Status and Neurobehavioral Development of Premature Infants

“…These authors suggested that altered myelination was the most likely explanation for their findings. 39,40 As the definition of abnormality of reflex in our study included latency, one possible explanation for our findings is impaired myelination in the low-iron group. However, in addition to latency, our definition also included the level of excitation.…”

“…However, in addition to latency, our definition also included the level of excitation. According to Roncagliolo et al, 39 differences in latencies and not in amplitudes may reflect altered myelination. Although we postulate that a delay in myelination is the most likely explanation for our findings, there is no way to confirm that this is the only mechanism.…”

Causas y consecuencias de la deficiencia de hierro

“…En lactantes de 6 meses de edad con anemia ferropriva la latencia o velocidad de la conducción nerviosa central del PAETC, desde la salida de la cóclea al lemnisco lateral del tronco cerebral se encontraba significativamente más lenta que en lactantes con nutrición de hierro adecuada. Al administrarles hierro medicinal por 6 meses, corrigiendo por completo la anemia, persistió esa diferencia al año y a los 18 meses de edad 49 . Más dramático es el hecho que a los 4 años de edad esta prolongación de la conducción nerviosa central persistía e incluso se proyectaba a los 6 años de edad (Figura 1).…”

Breast Milk Iron Concentrations may be Lower than Previously Reported: Implications for Exclusively Breastfed Infants

“…Indeed, there are researchers who are already recommending infants be supplemented with iron and several other vitamins and minerals [27,28]. The negative effects associated with ID in infancy have been well documented and the cognitive and psychomotor developmental setbacks may last well into childhood [29,30]. Indeed, the American Academy of Pediatrics recommends exclusively breastfed infants receive from irons at 4 month of age [31].…”